Extruding and filling containers made of foamed thermoplastic polymer

ABSTRACT

Method for the simultaneous extrusion and filling of expandable thermoplastic containers wherein the expandable thermoplastic material is extruded, clamping means gather and seal the foamed thermoplastic after it is extruded and while it is still in a state of plasticity so that the sealed area is formed by fusion of a foamed thermoplastic material, intermittently operated feed means fills the container after the seal is made and the substance being packaged causes inflation and shaping of the container, and clamp means is operative upon the deenergization of the feed means to effect a similar type seal for the other end of the container.

United States Patent 1151 3,696,179 Jacobs 1 Oct. 3, 1972 i541 EXTRUDINGAND FILLING 3,256,673 6/1966 Tew ..53/182 CONTAINERS MADE OF FOAIVIED3,331,902 7/ 1967 Stark ..264/99 THERMOPLASTIC POLYMER 3,399,508 9/ 1968Frielingsdorf ..53/140 [72] Inventor: William Jacobs 514 Grassy Hill2,575,138 11/ 1951 Slaughter 18/13 F X Road, Orange, Conn 064772,958,171 11/1960 Deckers ..264/99 UX 2,618,814 11/1952 Paton ..156/145[2 1 Filed: Oct. 15, 1970 3,425,185 2/1969 Samways ..53/182 21 A 1.N81099 1 pp 0 Primary Examiner.lulius Frome Related US. Application DataAssistant Examiner-Paul A. Leipold [63] Continuation-in-part of Ser. No.726,465, May 'Atmmey chnsten & Sabol 3, 1968, abandoned. ABSTRACT Methodfor the simultaneous extrusion and filling of 53/140, 53/182, 156/146,264/47, 264/ 5 expandable thermoplastic containers wherein the ex- 210,425/11 1, 1 425/317 pandable thermoplastic material is extruded,clamping [5 Cl. means gather and eal the foamed thermoplastic after 1Field of Search 164/173, 95, 47, 51, 45; it is extruded and while it isstill in astate of plasticity 156/145, 146; 53/29, 122, 140, 182; 18/1 Pso that the sealed area is formed by fusion of a foamed thermoplasticmaterial, intermittently operated feed [56] References C'ted means fillsthe container after the seal is made and the UNITED STATES PATENTSsubstance being packaged causes inflation and shaping of the container,and clamp means is operative upon 2,962,843 12/1960 Haelzer ..264/95 Xthe deenergization f the f d means to ff a 3,290, l LUX s v X imilar ealfor the other end of the container 1,242,562 10/1917 Laskey ..53/122 X2,576,444 1 l/1951 Clinefelter ..18/ 13 F X 9 Claims, 10 Drawing FiguresPATENTE'DUBI 3 I972 SHEET 1 BF 5 INVENTOR WILLIAM A JACOBS ATTORNEYS AM.I

LN- IL IL 9 03 M- M- 00 40 ami- 0Q 00 no 00 00 q INVENTOR WILLIAM A.JACOBS ATTORNEYS PATENTEDUCT 3 i972 SHEET 3 OF 5 INVENTOR WILLIAM A.JACOBS mwwm ATTORNEYS PATENTEDucI 3 I972 SHEET '4 BF 5 INVENTOR WILLIAMA. JACOBS ATTORNEYS PATENTED B S I972 v 3.696.179

sum s of 5 WILLIAM A. JACOBS MM*W ATTORNEYS EXTRUDING AND FILLINGCONTAINERS MADE OF FOAMED THERMOPLASTIC POLYMER This application is acontinuation-in-part of Ser. No. 726,465 filed May 3, 1968 and nowabandoned.

BACKGROUND OF THE INVENTION 1 Field of the Invention This inventionrelates to the method and apparatus for making, filling and sealingthermoplastic containers, and in particular, to such an arrangementutilizing expandable thermo-plastic material for the container.

cooling it, then heat-sealing one end thereof to form a container, andthen filling the container with the substance to be packaged. However,such known methods and/or apparatus have utilized a thermoplasticmaterial of the non-expandable type, have required some means forinflating, shaping and supporting the container, have required separateheating and/or cooling means for the extruded thermoplastic, and haveutilized various methods for evacuating the container before or duringthe filling thereof. Because of the complex apparatus and the controlstherefor, the known methods that have been used on a commercial basishave not permitted a high production rate andhave been uneconomical withrespect to the unit cost of the finished product.

; In the prior art mentioned above, a tube of unfoamed plastic must beinflated in order to form the container walls which then must be cooledprior to filling to strengthen the walls and to prevent the walls fromsticking to each other and/or the filling material. When the substancebeing packaged is a powder or liquid, the weight of the powder or liquidcoming into contact with the walls of an unfoamed plastic tube beforethe walls are adequately cooled could cause rupture of the tube. Inorder to cool the tube adequately so that this would not occur, the tubeis moved a very considerable distance from the extrusion die and coolingair is applied internally and externally. The use of cooling air onunfoamed thermoplastic containers also is necessary in the prior artbecause when such unfoamed thermoplastic material leaves the die head,it has little tensile strength and, until cooled, it would be uselessfor bagging purposes. Further complications ensue because the air usedfor cooling and inflating must be evacuated in order to fill the tube.If comminuted powder is the filling material, much of it goes out withthe air creating conditions of possible valve clogging, etc., inaddition to making the area generally dirty as well as wasting fillingmaterial, also, the resultant package is not a well-compacted one.

The prior art as exemplified by U.S. Pat. No. 3,343,216 disclosesmethods and apparatus for extruding a tube of foamable, expandablethermoplastic materials to provide foamed sheet material. But even inthis instance it is conventional to utilize air or some other gaseouselement as an inflating means. U.S. Pat. No. 3,290,198 discloses amethod and apparatus which comprises (1) extruding from an extruder anextrudable, foamable composition comprising a normally nonexplosive,synthetic organic polymer and a non-explosive concentration of a blowingagent, which is normally liquid under the pressure and temperatureexisting in the extruder and is normally gaseous under am- 5 bient(substantially atmospheric) pressure at the temperature of thecomposition as it leaves the extruder, to form a foamed tube; (2)cooling the interior surface of the tube, immediately after it leavesthe extruder, and expanding the tube, by means of a plug which ischilled by cooling water circulated through it and which has externaldimensions larger than the internal dimensions of the tube; (3) coolingthe exterior surface of the tube, immediately after it leaves theextruder, by means of air jets positioned completely around the externalperiphery of the tube; (4) at a distance from the extruder, pinchingspaced apart portions of the tube to form closed tetrahedron containersfilled with air. Heated pinching blades are necessary to close theportions of the tube because of the previous cooling steps and thedistance of the pinching blades from the extruder. The resultingcontainers then are separated by cutting with a knife and can be filledby piercing the wall with a needle and introducing filling fluid throughthe needle. No explanation is provided for removing air in thecontainers prior or during filling, although this is possible bypiercing the wall with another hollow needle. After filling, thecontainer is resealed by heating the nub, formed when inserting theneedle, to melt it and fill the hole formed by the needle.

SUMMARY OF THE INVENTION In practicing the present invention, a foamedthermoplastic tube is simultaneously made and filled with a substance tobe packaged by extruding a foamable thermoplastic material through anextrusion die to form a foamed hollow container, closing a portion ofthe hollow container immediately as it issues from the extrusion die,and feeding the substance to be packaged into the formed hollowcontainer as it is being extruded whereby the foamed hollow containerreceives the substance before permanent setting of the foamed hollowcontainer.

An object of this invention is to provide a method and apparatus formaking, filling and sealing tubular containers in the form of anextruded tube of foamed resinous material free of a longitudinal seam.

Another object of this invention is to construct a filled package offoamed thermoplastic that has little or no air space and has superiorqualities with respect to rigidity and cushioning than a similarly madepackage constructed of the same quantity of unfoamed or conventionalthermoplastic material.

The present invention has another object in that packaged materialdeposited within a tube is precluded from escaping during the packagingoperation.

It is another object of the present invention to construct a foamedthermoplastic tube without the need for cooling or inflating means andthus permit aseptic filling of a container.

The present invention has a further object in that progressive gatheringof the walls of a foamed thermoplastic tube into a decreasing crosssection permits the formation of an effective seal without heatingelements by merely utilizing the latent heat of the foamed thermoplasticmaterial, which seal substantially eliminates the possibility ofwicking.

An additional advantage of the present invention is the fact that thecontinuous flow of foamed plastic material is inflated, not by the useof air or other pressurized gas, but by the material itself which isbeing packaged. This is possible because of the unique qualities of thefoamed plastic and could not possibly apply to unfoamed thermoplasticmaterial because of its lack of tensile strength. For example, as thefoamable resinous material exists from the extrusion die, the immediaterapid internal expansion that takes place when the blowing agenttransforms from a liquid to a gas permits both inner and outer surfacesof the extruded tube to cool so rapidly that they are able to come im-'mediately into contact with other surfaces and materials withoutsticking. Moreover, this cooling effect serves to rapidly congeal thethermoplastic which thus rapidly gains strength. This particularcharacteristic permits a very important technique to be followed in thecase of filling finely comminuted powder items, such as activatedcarbon, talcum powder, dye pigments, cement, etc. into any container.This technique, which is common knowledge in the powder fillingindustry, is known as a bottom-up fill and is accomplished when the endof a powder filling auger or similar filling device comes into immediatecontact with the bottom of the container to be filled. As the augerstarts to feed powder, the container is pushed away from the end of theauger by the force of the fill of the powder. This results in agenerally firm package having a minimum amount of dust and fluffedmaterial and little or no air spaces. The same effect occurs in the caseof filling the foamed thermoplastic tube, and in fact, in an even moreefficient manner since the back pressure on the powder is not only inone direction but actually in all directions resulting in well-compactedcontents.

Other objects and advantages of the present invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial front elevationview of apparatus employed in the method of manufacture according to thepresent invention;

FIG. 2 is a side elevation view of FIG. 1;

FIG. 3 is an enlarged cross section taken along the line 33 of FIG. 1;

FIG. 4 is an enlarged cross section taken along line 44 of FIG. 8;

FIG. 5 is an enlarged elevation ofa detail of FIG. 1;

FIG. 6 is an end view looking from the left side of FIG. 5;

FIG. 7 is a cross section taken along line 77 of FIG.

FIG. 8 is an enlarged elevation with parts in section ofa detail in FIG.1;

FIG. 9 is a partial cross section taken along line 99 of FIG. 8 andshowing the initial sealing operation; and

FIG. 10 is an enlarged partial cross section taken along a line lookingin the direction of the arrows l0 10 of FIG. 9 but showing the finalsevering operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF APPARATUS As is illustratedin FIG. 1, the apparatus for performing the continuous filling andextruding method of the present invention, is embodied on a supportingrack 10 which is illustrated in a vertical position secured to a wallbut which may be self supporting and may even be in horizontal or otherplaner positions. A shaft 12 extending between a pair of sprockets l4and 15 is disposed on the top of the rack 10 while a similar shaft 16between sprockets 18 and 19 is disposed on the bottom of rack 10. Theshaft 16 has an extension which is connected to a suitable belt andpulley arrangement to a variable speed motor 20. An endless drive chain22 extends between the sprockets 14 and 18 on the left side and asimilar chain 23 extends between the sprockets 15 and 19 on the rightside.

A plurality of clamp carriers, indicated generally at 24, are secured tothe drive chains 22-23 for unitary movement therewith. As is shown inFIG. 2, six clamp carriers 24 are equally spaced around the periphery ofthe drive chain 23. The number of carriers may be varied in accordancewith particular operations. Inasmuch as the carriers 24 are identical instructure and function, the structural details of only one such carrierwill be described in detail.

Each carrier 24 includes a pair of spaced rods 26 and 28 secured ontheir left side by means of a plate 30 to the chain 22 and on theirright side by a similar plate 31 to the chain 23. A platform 32 (FIG. 5)is slidably mounted on the left side of rods 26 and 28 by means of frontand rear journal plates 34 and 36; centrally disposed between thejournal plates 34 and 36 and centrally located between rods 26 and 28 isa cam follower 38 perpendicularly extending from the undersurface ofplatform 32. A clamping or gathering element 40 has a laminatedconstruction with a central spacer 42 sandwiched between two sets ofplates; the first set of plates includes an inner plate 44, anintermediate plate 46 and an outer plate 48, while the second set ofplates similarly includes inner, intermediate and outer plates 50, 52and 54, respectively. The two sets of plates and the spacer 42 arefastened together as a unit by any suitable means, such as bolts andL-shaped brackets 56, to the top surface of platform 32 in edgewiserelation thereto. The inner plates 44 and 50 and the outer plates 48 and54 each have a triangular end 58 (FIG. 5) while the intermediate plates46 and 52 extend beyond the triangular ends 58 and are each providedwith a triangular notch 60; the ends 58 and notches 60 have identicalapex angles that intersect each other adjacent their apexes in atransverse plane defined by a bisector of the apex angle.

To facilitate an understanding of the structure forming mating parts ofthe clamp carrier 24, such mating parts are identified with odd numberedreference numerals which are next in sequence to the numerals for theircounterparts described above. For example, a second platform 33 isslidably mounted on the right side of rods 26 and 28 by means of frontand rear journal plates 35 and 37; centrally disposed between journalplates 35 and 37 and centrally located between rods 26 and 28 is a camfollower 39 perpendicularly extending from the undersurface of platform33. A second clamping or gathering element 41 has a laminatedconstruction with a central spacer 43 sandwiched between two sets ofplates; the first set of plates includes an inner plate 45, anintermediate plate 47 and an outer plate 49, while the second set ofplates similarly includes inner, intermediate and outer plates 51, 53and 55, respectively. The two sets of plates and spacer 43 are fastenedtogether as a unit by any suitable means, such as bolts and L-shapedbrackets 57, to the top surface of platform 33 in edgewise relationthereto. Intermediate plates 47 and 53 each have a triangular end 59(similar to the end 58 in FIG. 5), while inner plates 45 and 51 and theouter plates 49 and 55 extend beyond the triangular ends 59 and areprovided with triangular notches 61; the ends 59 and notches 61 haveidentical apex angles that intersect each other adjacent their apexes ina transverse plane defined by a bisector of the apex angle.

As is illustrated in FIG. 5, the two gathering clamps 40 and 41 areoppositely slidable by cam means to be described hereinafter. Thenotches 60 and 61 move toward each other while gathering a pliablematerial therebetween. Such movement ceases when the notches 60 on theintermediate plates 46 and 52 engage the edges on the triangular ends 59of the intermediate plates 47 and 53, and similarly when the notches 61on the inner and outer plates 45, 51 and 49, 55, respectively, engagethe edges on the triangular ends 58 of the inner and outer plates 44, 50and 48, 54.

A plunger rod 63 having an actuating roller 65 on its free end slidablyextends through the fixed spacer 43 for relative movement thereto. Theplunger rod 63 is centrally disposed through the spacer 43 and as shownin FIG. 7, upper and lower contact rods 67 and 69 are slidably extendingthrough the spacer 43. The contact rods 67 and 69 are current carryingconductors, the free ends of which have terminal lead wires forconnection to contact wipers 71 and 73, respectively, fixedly mounted onan extension of the outer strip 49 (see FIG. 8). Coil springs 75 and 73surround the outer ends of the contact rods 67 and 69, respectively, andare mounted in compression between the end face of spacer 43 andretainer nuts threaded onto the ends of the contact rods.

The inner end of the plunger rod 63 is fixed to a movable spacer block79 which is slidably disposed between the two inner plates 45 and 51.The upper and lower contact rods 67 and 69 are likewise fixed to thespacer 79 for unitary movement therewith so that the plunger rod 63, thecontact rods 67 and 69 and the spacer 79 move as a unit against the biasof the return springs 75 and 77 for a purpose to be describedhereinafter. The inner ends of contact rods 67 and 69 have conductorbrackets 81 and 83 protruding from the inner edge of the movable spacer79; and electrically heated cutting wire 85 spans the conductor bracketsand has its ends attached to tension springs 87 and 89, respectivelysecured to the upper and lower edges of the spacer 79.

Movement of the spacer ,79 is effected by the roller 65 engaging anincreasingly sloped cam surface 91 located on the center leg of acontactor-cam unit 93 which is vertically secured to an end portion ofthe frame by a pair of spaced mounting rods 95-95 (FIG. 2 and 10). As isshown in FIG. 3, the contactor cam unit has a generally mirrored E shapewith a pair of contactor strips 97 and 99 fixed between the center legdefining the cam surface 91 and the respective end legs. The contactorstrips 97 and 99 are electrically connected to a suitable power source(not shown).

The gathering clamps 40 and 41 are reciprocated relative to each otherby means of their cam followers 38 and 39 following the contour ofequally spaced cam tracks fixed to the frame 10. As is shown in FIG. 1,the two cam tracks have entrance sections 100 and 101 respectivelyreceiving the left cam follower 38 and the right cam follower 39,converging sections 102 and 103, straight sections 104 and 105,diverging sections 106 and 107, and exit sections 108 and 109.

Centrally mounted on the top portion of the frame 10 is a feed andextruder unit including a die body 110 having a side conduit 112 openinginto a cylindrical die annulus 114 (see FIG. 4). As viewed in FIG. 8,the annulus 114 communicates with an annular die ring 116 adjustablyfixed to the die body 110 by any suitable means, such as cap screws (notshown). The inner surface of the die ring 116 is frusto-conical in shapeto conform to a corresponding shape on the adjacent end of a cylindricaldie core 118; the lower inner periphery of the die core 118 is engagedby an insulating spacer ring 120. The upper end of the die core 1 18extends out of the die body 110 and is adjustably fixed thereto by athreaded nut 122 that permits adjustment of the die orifice. A lockingcollar 124 is fixed to upper edge of the die core and defines an uppersupport guide for a feed tube 126 while the insulating spacer ringdefines a lower support guide for the tube 126. A dead air space is thusformed between the tube 126 and the die core 118 to serve as a heatinsulator. An auger 128 is operatively disposed in the tube 126 and inthe present .arrangement is adapted to the driven intermittently by anysuitable drive motor (not shown).

The material to be packaged is centrally fed by the auger 128 into afoamed thermoplastic container being concentrically extruded as shown at1 18. The container 130 is gathered by the clamps 40 and 41 in two areasdefined by the mating first and second sets of plates; i.e., the secondset of plates 50, 52 and 54 on clamp 40 mesh with the second set ofplates 51, 53 and 55 on clamp 41 to gather and clamp the extrudedplastic by means of the notches 60 and 61 into a lower sealed portion132, and similarly, the first set of plates 44, 46 and 48 on clamp 40mesh with the first set of plates 45, 47 and 49 on clamp 41 to gatherand clamp the extruded plastic by means of the notches 60 and 61 into anupper sealed portion 134. As is apparent from FIGS. 1 and 10, the twosealed portions 132 and 134 are spaced from each other and are severedby the cutting wire 85 with the lower sealed portion 132 defining theclosed top of a completed container 130 and the upper sealed portion 134defining the closed bottom of the subsequently extruded container 130.

METHOD AND OPERATION The steps of manufacture according to the presentinvention will be described in their proper order in the followingdescription of a sequence of operation of the above apparatus. Anysuitable foamable thermoplastic material may be utilized, e.g., one ofthose mentioned in US. Pat. No. 3,343,216, the disclosure of which isincorporated herein by reference.

Suitable foamable thermoplastic materials or compositions contain anormally non-explosive, synthetic organic, thermoplastic polymer orresin and a non-explosive concentration of a foaming or blowing agent.The thermoplastic polymers or resins which can be extruded according tothe invention include cellulose ethers and esters, e.g., ethylcellulose, cellulose acetate, cellulose acetate-butyrate, homopolymersand interpolymers of monomer compounds containing the CH C grouping,such as olefins, e.g., ethylene, propylene, isobutylene, butene-l, vinylhalides, e.g., vinyl chloride; vinylidene chloride; vinyl esters ofcarboxylic acids, e.g., vinyl acetate, vinyl stearate, vinyl benzoate,vinyl ethers, e.g., vinyl methyl ether, vinyl ethyl ether, vinylisobutyl ether; chlorotrifluoroethylene, tetrafluoroethylene,hexafluoropropylene, unsaturated carboxylic acids andderivativesthereof, e.g., acrylic acid, methacrylic acid, methylacrylate, ethyl acrylate, methyl methacrylate, acrylamide,acrylonitrile, methacrylonitrile, and interpolymers of theabovementioned vinylidene monomers with alpha, beta-unsaturatedpolycarboxylic acids and derivatives thereof, i.e., maleic anhydride,diethyl maleate, dibutyl fumarate, diallyl maleate, dipropyl maleate,etc. A preferred class of materials with which optimum results areobtained are rigid, relatively non-elastic, thermoplastic resins, suchas homopolymers and interpolymers of vinyl chloride, e.g., polyvinylchloride, vinyl chloride-vinyl acetate copolymer (87:13), vinylchloride-acrylonitrile copolymer (80:20); homopolymers of vinylidenearomatic hydrocarbons and ring halogenerated derivatives thereof, e.g.,styrene, o-chlorostyrene, p-methylstyrene, p-ethylstyrene,alpha-methylstyrene, vinyl naphthalene and interpolymers of suchvinylidene monomers with each other and with other vinylidene monomersin which the interpolymer contains at least 70 percent of the vinylidenearomatic hydrocarbon compound, e.g., a copolymer of 70 percent styreneand 30 percent acrylonitrile. One of the preferred class of resins isthermoplastic styrene polymers containing at least 70 percent by weightof styrene in the structure.

Unless otherwise indicated, all parts and percentages are by weight.

When employing polystyrene there can be employed normal crystal gradepolystyrene or high impact polystyrene or a mixture containing to 95percent normal crystal grade polystyrene and the balance high impactpolystyrene. When employing a thermoplastic styrene polymer it normallycontains greater than 50 percent by weight of styrene and preferably atleast 70 percent by weight of styrene in its structure. High impactpolystyrenes are frequently prepared by polymerizing monomeric styrenein the presence of 2% to 10 percent by weight of a rubbery diene polymeror by polymerizing styrene in the presence of such amounts of adifunctional material. Examples of high impact styrene include aterpolymer of 5 percent acrylonitrile, 5 percent butadiene and 90percent styrene; a copolymer of 5 percent butadiene and 95 percentstyrene; the product made by polymerizing 95 percent of styrene in thepresence of 5 percent of polybutadiene; a copolymer of 5 percentchlorosulfonated polyethylene and 95 percent styrene; a blend of 97.5percent polystyrene and 2.5 percent polybutadiene; a blend of 95 percentpolystyrene and 5 percent hydrogenated polybutadiene containing 35.4percent residual unsaturation; polystyrene formed in the presence of 5percent hydrogenated polybutadiene containing 4.5 percent of residualunsaturation, a blend of 95 percent polystyrene and 5 percentpolyisoprene, and a copolymer of 99.5 percent styrene and 0.5 percentdivinyl benzene.

Other suitable thermoplastic resins include polycarbonates, e.g. thepolymer from bisphenol-A and diphenyl carbonate; polyoxymethylene(Delrin), oxymethylene-alkylene oxide copolymers, e.g.oxymethylene-alkylene oxide (95:5); polyurethanes, e.g. from toluenediisocyanate and polypropylene glycol molecular weight 2,025; Dacron(polyethylene terephthalate), nylon (e.g., polymeric hexamethyleneadipamide). ABS terpolymers can be used, e.g., the terpolymer of 25percent butadiene, 15 percent acrylonitrile and percent styrene (a rigidABS terpolymer), as well as other terpolymers containing 25 to 60percent butadiene, 10 to 20 percent acrylonitrile and 20 to 60 percentstyrene.

The invention is of particular value with foams from polyethylene (ofhigh density, e.g., 0.960, medium density, e.g., 0.935 or low density,e.g., 0.914), polypropylene, copolymers of ethylene and propylene (e.g.,50-50 copolymer) and regular or high impact polystyrene. Copolymers ofethylene with butene-l (e.g., 9: 10) also can be employed.

To insure the formation of a uniform, foamed portion or core anucleating agent should be used in forming the foamed container. When anucleating agent is employed, it is used in an amount of from 0.02 to 10percent of the total polystyrene by weight. Preferably, 0.4 to 2 percentof the nucleating agent is used.

Conventionally, the nucleating agents are made up of two materials whichreact to form carbon dioxide and water. The two materials are normallyused in approximately equivalent amounts. As the carbon dioxideliberating materials there can be used ammonium, alkali and alkalineearth carbonates or bicarbonates, e. g., ammonium bicarbonate, sodiumbicarbonate, sodium carbonate, potassium bicarbonate, calcium carbonate.The other material is an acid or acid-reacting salt, preferably solid,which is sufficiently strong to liberate the carbon dioxide from thecarbonate or bicarbonate. Generally, the acid has at least 3.0milliequivalents of acidic hydrogen, and preferably at least 10.0milliequivalents, per gram. The acid can be organic or inorganic.Suitable acidic materials include boric acid, sodium dihydrogenphosphate, fumaric acid, malonic acid, oxalic acid, citric acid,tartaric acid, potassium acid tartrate, chloroacetic acid, maleic acid,succinic acid and phthalic acid. In place of the anhydrous acids orsalts there can be used the solid hydrates, e. g., oxalic acid dihydrateand citric acid monohydrate.

While not essential, there can also be added a wetting agent such asBayol 35 (a petroleum aliphatic hydrocarbon white oil), kerosene havingan average of at least eight carbon atoms in the molecule,alkylphenolalkylene oxide adducts, e.g., Triton X-lOO(t-octylphenol-ethylene oxide adduct having 10 ethylene oxide units inthe molecule), sodium lauryl sulfate and sodium dodecylbenzenesulfonate. The wetting agent can be nonionic or anionic.

A foaming or blowing agent is incorporated into the thermoplasticpolymer. Preferably the foaming agent is dispersed throughout thepolymer, for example, in the manner taught by US. Pat. Nos. 2,941,964;2,864,778; 3,026,273; 3,026,272; 3,026,274; and Canadian Pat. No.682,464, the disclosures of all of which are incorporated herein byreference.

Thermoplastic polymers containing foaming agents are availablecommercially.

The foaming agent is normally liquid under the temperature and pressureexisting in the extruder and is normally gaseous under ambient(atmospheric) pressure at the temperature of the composition immediatelyas it leaves the extruder. The foaming agent should be non-reactive withthe polymer and, in the low concentrations used, should have not morethan a slight solvent action on the polymer. Suitable foaming agentsinclude aliphatic hydrocarbons boiling between 10 and 100 C. andpreferably between 30 and 90 C., e.g., petroleum ether (containingprimarily pentane or hexane or a mixture of these hydrocarbons),pentane, hexane, isopentane, heptane, cyclohexane, cyclopentane,pentadiene and neopentane. Other volatile liquids include methanol,ethanol, methyl acetate, ethyl acetate, butane, acetone, methyl formate,ethyl formate, dichloroethylene, perchloroethylene,dichlorotetrafluoroethane, isopropyl chloride, propionaldehyde,diisopropyl ether, dichlorodifluoromethane, a mixture of pentane with to30 percent of methylene chloride or other volatile lower halogenatedhydrocarbon. Usually, the amount of foaming agent will be 0.1 to 15percent by weight of the polymer, e.g., polystyrene to be expanded. Theamount of foaming agent will depend upon the extent of foaming desired.In general, the greater the amount of foaming agent in the polymermixture the more the expansion. It has been found that good expansioncan be obtained using very small amounts of the foaming agent.

Another mode of incorporating the foaming agent into the polymer is bypremixing the pelletized, solid, thermoplastic polymer, e.g., highimpact styrene polymer, with a minor amount of an absorbent havingabsorbed thereon, the foaming agent which is nonreactive with and whichhas not more than a slight solvent action on the polymer. The foamingagent should volatilize below the softening point of the polymer.

As the absorbent there can be employed any conventional absorbent infinely divided form, such as diatomaceous earth (Celite), fullers earth,silica gel, e.g., Cab-O-Sil and l-li-Sil, activated alumina, molecularsieves, attapulgus clay and activated carbon. The absorbent is usuallyused in an amount of 0.1 to 15 percent, preferably, 0.5 to 10 percent byweight of the polymer, although up to 25 or 30 percent of absorbent canbe employed. The absorbent is an inert filler of large surface area butsmall particle size, e.g., 200 mesh or below.

The amount of foaming agent absorbed on the absorbent can vary from 5 to150 percent or more based on the weight of the absorbent. The amount offoaming agent absorbed will depend upon the capacity of the absorbentfor the particular foaming agent. Normally, the absorbent containing thefoaming agent will appear to be a dry powder. The foaming agent employedshould be one which is non-reactive with the particular polymeremployed.

The technique and conditions for extruding the foamable thermoplasticcomposition to form a foamed tube are well known and are disclosed in,for example, US. Pat. No. 2,917,217; 3,290,198; 3,343,216 and 3,151,192the disclosures of all of which are incorporated herein by reference.Any of the techniques and conditions disclosed in these patents can beused in the present invention except that cooling or chilling meansother than ordinary atmospheric conditions are not applied to the tubeas it issues from the extruder nor is the tube blown or expanded by air,other gaseous means or by a plug.

The foamable thermoplastic composition is fed to the hopper of anextruder and is passed through the extruder wherein it isheat-plasticized under pressure and is forced under pressure out of theannular die of the extruder in the form of a tube. Upon entering theatmosphere, the blowing agent flash evaporates to foam the walls of thetube and at the same time automatically cools the surfaces of the wallsof the tube somewhat to impart some rigidity but not sufficiently tofully congeal the walls throughout. In this condition the surfaces ofthe tube wall are cooler than the inner portions and are relativelynon-sticky. The tube walls are hot enough, however, to be formed, forexample, by expansion with the filling substance, and set by subsequentcooling below the setting temperature of the thermoplastic composition.

Specific temperatures and pressures within the extruder depend primarilyupon the specific thermoplastic polymer being extruded. Temperatureswithin the extruder, however, usually can range from about 200 F. toabout 375 F., preferably from about 250 F. to about 325 F. and pressureswithin the extruder can range from about psig to about 5,000 psig,preferably about 500 psig to about 2,500 psig, more preferably about 700psig to about 1,500 psig. The conditions in the extruder are selected toheatplasticize the foamable thermoplastic composition and cause it toflow through the orifice of the extrusion die. It is most beneficial tomaintain sufficient pressure on the composition while it is in theextruder and die so that, at the temperatures existing therein, only asmall amount, or none, of the foamable composition is allowed to foamprior to being extruded through the annular orifice.

When the tube issues from the die orifice, a portion of it is closed,e.g., through gathering and compressing by the clamps, as close aspossible to the die orifice, for example, within 18 inches, preferablywithin 12 inches or less from the orifice. At the point of closing, thetube is still hot enough to be formed and sealed to itself under thepressure of the clamps without the application of external heat. Closingis performed on those portions of the tube which are still a state ofplasticity to form fused hermetic seals at said closed ends. The

closing step is carried out before the tube has cooled throughout to atemperature below its plasticity temperature, that is, the temperatureat which-the tube is capable of plastic flow under the pressure of theclamps (e.g., about to 5,000 psi) to form a seal which can be set bycooling. The plasticity temperature is in and above the softening pointrange of the thermoplastic composition and usually is higher than thetemperature at which the thermoplastic composition gels, congeals orsets. The plasticity temperature depends primarily upon the nature ofthe thermoplastic composition,

As the thermoplastic composition issues from the die its internal (core)temperature is preferably below about 325 F., e.g., about 200 F to about275 F. and the interior surface temperature is somewhat lower, perhapsabout 1 to about 50 F. lower. At the point where portions of the tubeare closed by the clamps,

the internal temperature is still lower, perhaps another 1 to 50 F.lower than adjacent the die orifice, and the interior surfacetemperature is still somewhat lower, perhaps another 1 to 50 F. lowerthan adjacent the die orifice. The temperature of the interior surfacewhich is contacted by the filling substance, therefore varies from theinterior surface temperature of the tube as it issues from the die andthe interior surface temperature of the tube at the point where it isgathered and compressed by the clamps.

The thickness of the tube walls as it issues from the die orifice is notnarrowly critical. The walls of the tube as it issues, are in anexpanding or foaming condition. The radial thickness of the orifice isnot narrowly critical and can vary from about 0.005 or less to about0.15 inch or more. After leaving the orifice, the tube walls foam orexpand to a thickness of, for example, about 0.02 or less to about 0.75inch or more. The thickness can be reduced by the draw down rate, i.e.,the excess of the rate by which the clamps are pulling the tube over therate at which the tube is being extruded and the expansion of theoverall lateral dimensions of the tube by the filling substance. Thethickness of the tube walls of the finished, sealed package can rangefrom about 0.01 to about 0.75 inch or more.

The foamable thermoplastic material is continuously fed into the conduit112 which represents a high pressure zone and is extruded from theannular die ring 116 to the atmosphere representing a low pressure zone.As is well known in the art, the foamable thermoplastic is in a heatedcondition permitting it to flow through the die body. While the dieorifice may have any desired shape, it is illustrated as being circularin this instance. The chain drive 22-23 is also continuously operatedbut the auger 126 is intermittently operated to permit closure of thecontainer 130 before filling with the substance to be packaged.

As is illustrated in FIGS. 1 and 2, the clamp carrier 24 traverses thesupport frame 10 with its cam followers 38 and 39 in the cam tracks.Entry of the cam followers 38 and 39 into the converging sections 102and 103 causes inward movement of the clamps 40 and 41 toward eachother; due to the mating notches 60 and 61, the extruded thermoplasticis being gathered therebetween. When the extruded thermoplastic leavesthe die orifice, it is moved to a lower pressure and temperature causingit to be expanded into a foamed condition; at this time, the internalportions or core of the foamed thermoplastic is still in a state ofplasticity due to the latent heat remaining in the foamed thermoplastic.The notches 60 and 61 progressively gather the foamed thermoplasticwhile it is still in its state of plasticity, into an ever decreasingcross section and compress the same with increasing pressure as theclamps 40 and 41 move closer together. When the cam followers 38 and 39reach the straight sections 104 and 105, the foamed thermoplastic iscompressed with such force as to fuse the same and define hermetic sealsfor the container; the fused seals are possible because the clamps areactuated while the internal portions or core of the foamed thermoplasticare still in a state of plasticity. Because of the first and second setsof plates on the clamps 40 and 41, the foamed thermoplastic is sealed attwo areas 132 and 134 (FIGS. 9 and 10) spaced from each other by thedimension of the spacers 42 and 43.

The hermetic seal 134 represents the closed bottom of the container 130which is now ready for the filling operation. By suitable controlcircuitry (not shown) the auger 128 is operated as the cam followers 38and 39 leave the converging cam tracks 102 and 103. The container 130 isnow being filled as the clamp carrier 24 moves downwardly along the camsections 104 and 105. The filling material itself causes the inflationof the container l30 because of the plastic internal condition thereofas it is extruded from the die orifice. During this time, the clamps 40and 41 remain engaged at the hermetic seals 132 and 134 whereby thecontainer 130 is advanced during its continuous extrusion. A particularadvantage of this arrangement is that there is no need for anysupporting structure or mold for the container 130; the rate of movementof the clamp carrier 24 is one of the variables that determines thethickness of the wall of the container 130. The walls of the containercan be made thinner by adjusting the rate of movement of the clampcarrier 24 to be faster than the rate of extrusion of the container 130.

During downward movement of the clamp carrier 24 as viewed in FIG. 1,the contact wipers 71 and 73 engage the contactor strips 97 and 99,respectively, to complete a circuit for the cutting wire 85. When theclamp carrier 24 approaches the lower end of the conductor in the camunit, the roller 65 is in engagement with the increasing slope of thecam surface 91 which causes inward movement of the movable spacer 79 andthe heated wire 85; as shown in FIG. 10, the heated wire 85 severs thatportion of the clamped end between the hermetic seals 132 and 134. Justbefore the roller 65 leaves the cam surface 91, the next clamp carrier24 has its cam followers 38 and 39 entering the converging sections 102and 103 at which time the control circuitry deenergizes the auger 128and the cycle is repeated. When the roller 65 leaves the cam surface 91the movable spacer 79 and the attached heated wire 85 are retracted totheir original position under the bias of the springs and 77; thecontact wipers 71 and 73 leave the contact strips 97 and 99 at this timecausing deenergization of the heated wire It should be noted that theseverance between the hermetic seals 132 and 134 does not release thelowermost container 130 at this time because the cam followers 38 and 39are still in the straight sections 104 and 105 of the cam tracks. As thecam followers 38 and 39 move into the diverging sections 106 and 107,the clamps 40 and 41 are moved away from each other whereupon the lowercontainer is released to fall onto a suitable conveyor or a shippingcarton. The cam followers 38 and 39 then proceed into the exit sections108 and 109 so that the closed bottom 134 of the subsequently formedcontainer 130 is also released but such container 130 is supported insuspension by the next clamp carrier 24 which has clamped and sealed theextrusion to form a closed top for the container.

The spacing between the clamp carriers 24 determine the size of thecontainers to be extruded. Thus, when the heated wire 85 is performingthe cutting operation on the lowermost part of the container, thecontrol circuitry has deenergized the auger 128 so as to stop thefilling operation. However, the extrusion continues so that the nextclamp carrier 24 has its cam followers entering the converging sections102 and 103 to perform the clamping and sealing operation as describedabove.

Inasmuch as the container 130 is made of foamed thermoplastic, it hassufficient rigidity so as to be utilized for large industrial packagingapplication, e.g., a package containing fifty pounds of powder, soap,etc. In addition, the filled container 130 has sufficient resiliency toprovide its own cushioning effect and thus eliminate the need forcellular type crating for shipping purposes.

EXAMPLE Homopolymeric polystyrene pellets, containing percent pentane,about 0.5 percent sodium bicarbonate, and about 0.5 percent citric acid(percentage based on the weight of polystyrene) was fed through a hopperto the feed end of an extruder. The extruder screw, 2 inches in diameterhad a length to diameter ratio of /1 consisting of three constant pitchflight sections; namely, a feed section about one-half the length of thescrew, a transition section about onefourth the length of the screw, anda metering section about one-fourth the length of the screw. Theextruder barrel was heated to approximately 250 F. at the feed section,280 F. at the transition section, 280 F. at the metering section and 260at the cross-head die. The exit orifice of the cross-head was one andthree fourths inches in diameter with a circular opening of 0.020 inchthickness. The center of the cross-head mandrel had been bored out to adiameter of one and five eighths inches through which activated carbonpowder would be metered as shown in FIG. 8. Upon emerging from the diethe polystyrene foamed into a foamed unicellular seamless tube and'waslater expanded by the force of the carbon powder pressing against theinterior walls of said tube as described below. A pair of jaws convergedon the tube, progressively gathering the circular wall and compressingit to a cross section whose area was approximately three-sixteenths ofan square inch. The temperature of the tube during sealing was about 240F. Immediately after thus sealing said tube, the filler auger (128 FIG.8) was rotated, rapidly feeding the carbon powder into the interior ofthe tube, expanding it to approximately 4 inches in diameter. Thetemperature of the inner surface of the tube contacted by the carbonranged from about 160 F. to about 180F. The wall thickness wasapproximately 0.090 inch after expansion and draw down. After apredetermined number of rotations (38 in this case) of the augur hadbeen made, the rotation ceased, the

augur. having deposited the desired amount of powder into the package byvirtue of its positive displacement design. The next set of jaws at thattime sealed the package in the same manner as the prior set of jaws,thus completing the sealing of the package. The linear rate of speed ofthe jaws in the direction of extrusion was 25 feet per minute,sufficient to exceed the linear rate of flow of the plastic extrudate 20feet per minute) as it exited from the die orifice, causing a desirabledrawing down of the foamed plastic to control the wall thickness of thefinished package. Cutting of the packages was accomplished by use of thehot wire FIG. 8) in the seal area. The center to center distance ofseparation of the pairs of jaws was 12 inches, the production rate ofthe machine was 1,500 packages per hour, the weight of the package was15 grams and the weight of the contents was 12 ounces.

Even though the foregoing description has mentioned comminuted materialsas the substance to be packaged, it is to be understood that a fluid,such as a liquid detergent, may also be the packaged material. In suchan instance, the feed means would be in the form of a check valve at thebottom of the tube 126 and an on-off valve at the top. Because of thefused seals 132 and 134 described above, the use of a liquid as thesubstance to be packaged becomes more acceptable than methods usedheretofore. The fused seals 132 and 134 eliminate any possibility ofwicking that is prevalent in the known prior art methods.

In accordance with the present invention, there is no need for a coolingagent or device and the substance being packaged is not exposed to theatmosphere or to any type of contamination. This feature permits themaking of sterilized packages and an aseptic package is particularlyadvantageous to the drug industry for packaging drugs and to the dairyindustry for packaging milk, cheese, etc.

Typical of comminuted materials that can be packaged according to themethod of this invention are powdered, activated charcoal such as isused in the dry cleaning industry, powdered silica fillers used asreinforcing agents in the plastics industry, other powdered or granularmaterials, such as, powdered granulated dyestuffs, sodium bicarbonate,sodium chloride, calcium chloride, soap and detergent powers, powderedsurfactants, powdered or granulated metals, such as, iron, nickel andtin powders, or granules, coffee granules, instant coffee powder orgranules, and the like. Typical liquids that can be packaged accordingto this invention include liquid detergents, motor oil, water, milk,fruit and vegetable juices, soups, soft drink concentrates, liquidsurfactants, liquid dyestuffs, and the like. The present invention canbe used to package any liquid, powder or granulated substance which isinert to the thermoplastic polymer and is normally non-explosive underconditions existing within the tube of polymer as it leaves theextruder, and especially applies to those substances that are inert tothe thermoplastic polymers and non-explosives at temperatures belowabout 400 F.

Inasmuch as the present invention is subject to many modifications,variations and changes in details, it is intended that all mattercontained in the foregoing description or shown on the accompanyingdrawings, shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. In the method of making foamed thermoplastic polymer containers whichcomprises extruding from an extruder an extrudable, foamable compositioncomprising a normally non-explosive, synthetic organic thermoplasticresin made from a monomer selected from the class consisting of olefins,vinyl halides, vinylidene aromatic hydrocarbons and ring halogenatedderivatives thereof, and a non-explosive concentration of a blowingagent, which is normally liquid under the pressure and temperatureexisting in the extruder, and is normally gaseous under atmosphericpressure at the temperature of the composition immediately as it leavesthe extruder, to form a foamed tube, and closing portions of said tubeto form the container, that improvement in making, filling and sealingsaid container to form sealed containers filled with a substance whichis substantially inert to said polymer and normally nonexplosive underconditions existing within said tube as it leaves the extruder,comprising the steps of,

1. closing a portion of said tube by fusing its inner walls togetherbefore it cools throughout to a temperature below its plasticitytemperature to form a bottom closed end,

2. feeding said substance to be packaged into said foamed tubeimmediately upon formation of said bottom closed end to fill and expandsaid foamed tube before it cools throughout to a temperature below itssetting temperature,

3. closing a succeeding portion of said foamed tube by fusing its innerwalls together before it cools throughout to a temperature below itsplasticity temperature to form a top closed end.

2. The invention as recited in claim 1 wherein the substance to bepackaged is a comminuted material.

3. The invention as recited in claim 1 wherein the substance to bepackaged is a liquid material.

4. The invention as claimed in claim 1 wherein said thermoplastic resinis made from styrene.

5. The invention as recited in claim 4 wherein the bottom closed end andthe top closed end are simultaneously formed from the continuouslyextruded thermoplastic with the bottom closed end being on the tubeportion to be filled and the top closed end being on the tube portionthat has been filled.

6. The invention as recited in claim 5 wherein the simultaneously formedclosed ends are separated by an unsealed portion, and said unsealedportion is severed to permit removal of the resulting filled container.

7. The invention as recited in claim 4 wherein, during said feedingstep, said tube is expanded to a predetermined diameter by forcing aselected volume of said substance into said tube.

8. The invention as recited in claim 7 wherein said tubing is supportedsolely at its closed one end during its expansion.

9. Invention as claimed in claim 4 wherein at least one of said closingsteps is performed by gathering a portion of said tube and reducing thecorss section of the gathered portion to fuse it and form a hermeticseal.

2. feeding said substance to be packaged into said foamed tubeimmediately upon formation of said bottom closed end to fill and expandsaid foamed tube before it cools throughout to a temperature below itssetting temperature,
 2. The invention as recited in claim 1 wherein thesubstance to be packaged is a comminuted material.
 3. The invention asrecited in claim 1 wherein the substance to be packaged is a liquidmaterial.
 3. closing a succeeding portion of said foamed tube by fusingits inner walls together before it cools throughout to a temperaturebelow its plasticity temperature to form a top closed end.
 4. Theinvention as claimed in claim 1 wherein said thermoplastic resin is madefrom styrene.
 5. The invention as recited in claim 4 wherein the bottomclosed end and the top closed end are simultaneously formed from thecontinuously extruded thermoplastic with the bottom closed end being onthe tube portion to be filled and the top closed end being on the tubeportion that has been filled.
 6. The invention as recited in claim 5wherein the simultaneously formed closed ends are separated by anunsealed portion, and said unsealed portion is severed to permit removalof the resulting filled container.
 7. The invention as recited in claim4 wherein, during said feeding step, said tube is expanded to apredetermined diameter by forcing a selected volume of said substanceinto said tube.
 8. The invention as recited in claim 7 wherein saidtubing is supported solely at its closed one end during its expansion.9. Invention as claimed in claim 4 wherein at least one of said closingsteps is performed by gathering a portion of said tube and reducing thecorss section of the gathered portion to fuse it and form a hermeticseal.